Regeneration mechanism of Pt/BaO/Al2O3 lean NOx trap catalyst with H2
Regeneration mechanism of Pt/BaO/Al2O3 lean NOx trap catalyst with H2
复制标题
DOI：
10.1016/j.cattod.2008.01.007
复制
发表时间：
2008-07
期刊：
影响因子：
5.3
通讯作者：
S. Mulla;S. S. Chaugule-S.;A. Yezerets;N. Currier;W. Delgass;F. Ribeiro
中科院分区：
文献类型：
--
作者：
S. Mulla;S. S. Chaugule-S.;A. Yezerets;N. Currier;W. Delgass;F. Ribeiro
以H_2为模型还原剂，对铂/BaO/Al_2O_3NO_x储存还原催化剂的再生进行了研究。我们认为，再生过程涉及还原剂的局部反应前沿，该反应前沿通过催化剂床层，使捕获位置完全再生。当用NH_3代替H_2作为再生气时，再生过程与用H_2相当，在再生捕集催化剂方面，NH_3和H_2一样有效。该过程仅受氢原子供应的限制，与氢源(H_2或NH_3)无关，也不受温度变化或CO_2和H_2O存在的影响。尽管铂本身在将NOx/H_2进料流中的NOx还原为N_2方面没有很高的选择性，但由于不受欢迎的副产物，主要是NH_3，继续进一步反应，直到它们被最佳地转化为N_2，因此在含Ba的捕集催化剂上保持了高的N_2选择性。事实上，我们认为，以H_2为还原剂的陷阱催化剂的再生涉及到从储存的NOx中生成作为中间体的NH_3，并且NH_3作为H原子的载体。NH3最终被储存的NOx进一步氧化成N2，NOx是催化剂上的氧源，对N2有很高的选择性。
Regeneration of a Pt/BaO/Al2O3NOxstorage-reduction catalyst was studied using H2as a model reductant. We propose that the regeneration process involves a localized reaction front of the reductant that travels through the catalyst bed with complete regeneration of the trapping sites. When NH3was used as a regenerating gas instead of H2, the process was found to be equivalent to that with H2, and NH3was found to be as effective as H2in regenerating the trap catalyst. The process was limited only by the supply of the hydrogen atoms, irrespective of the source of hydrogen (H2or NH3) and was also not affected by temperature changes or by the presence of CO2and H2O. Even though Pt by itself is not very selective in reducing the NOxto N2in a NOx/H2feed stream, a high N2selectivity is maintained over the Ba-containing trap catalyst since the undesirable byproducts, mainly NH3, continue to react further until they are optimally converted to N2. In fact, we propose that the regeneration of the trap catalyst using H2as the reductant involves the formation of NH3as an intermediate from the stored NOx, and NH3acts as a carrier of H-atoms. The NH3ultimately gets further oxidized to N2by the stored NOx, the oxygen source on the catalyst, giving high selectivity towards N2.